This invention relates in general to belt driven X-Y component positioning systems, and more particularly, to a lugged belt and lugged pulley driven linear X-Y positioner.
Many machines have systems for linear positioning of work pieces and various other articles to perform work such as assembly, testing, packaging, palletizing, welding, bonding, dispensing, etc. Most linear positioning used today requires at least some form of remote control permitting the rate of movement, accelerations and positioning accuracy to be remotely controlled and predictable. The technology of many linear positioning systems is quite old such as shown with many examples including milling machines and other machine tools. Machines such as these use heavy, precision made components to provide a means to drive and guide an object in a straight line and motor driven screws power driving objects in their movements. Many new drive components that have become available in recent years provide many design opportunities for drive system improvements. Stepping motors, for example, are now available with positioning capabilities as high as twenty five thousand steps per revolution of the motor output shaft to thereby permit linear drive systems a greater range of drive design considerations in more direct methods of power conversion (as opposed to conventional lead screws and/or gear drives) while maintaining considerable resolution. Another advantage with more direct drives is that they permit the motor drive to operate at a lower frequency providing higher linear positioning speeds and reduced noise levels. One direct drive approach is the use of a timing belt driven directly by a timing belt pulley attached to the motor shaft. Heretofore, the disadvantage of such a drive is that if the timing belt becomes very long the elasticity thereof causes some hysteresis in the drive system directly reducing positioning accuracy. It should be noted that with a timing belt drive (i.e. lugged belt and pulley drive) that hysteresis error is directly related to the linear force required to move the load and the length of the timing belt.
It is therefore a principal object of this invention to provide a lugged belt and pulley drive with high positioning accuracy.
Another object with such a lugged belt drive is to minimize hysteresis and the effect of hysteresis in the drive system.
A further object is to provide such belt drive improvements in a lugged belt driven positioning X-Y positioning system.
Still another object is to provide such a lugged belt driven X-Y positioning drive divided into three sectors having high positioning accuracy in a relatively low cost drive system.
Features of the invention useful in accomplishing the above objects include, in a lugged belt and pulley X-Y article positioned drive system, a two axis drive lugged belt and lugged pulley drive system driving a driven member independently in two, mutually perpendicular axes with the drive in each direction operational alone or simultaneously for vector movement of the driven member. Both X-Y axis are directly belt-driven by respective motors and with the axis considered "Y" the primary hysteresis minimizing drive is directed primarily to the lugged belt of substantial length in the "Y" axis. This is with the "Y" drive lugged belt routed around six pulleys to move the "X" axis carriage mounting and guide structure, with the belt attached at two points, at opposite sides of one end of the "X" axis carriage mounting and guide structure. The drive motor for the "Y" drive lugged belt is directly coupled to one of the six pulleys that is gear meshed to another of the six pulleys assuring precise synchronous counter-rotation of the paired set of pulleys at one corner of the "Y" drive. There is a second set of gear meshed pulleys at an "X" direction displaced corner from the corner set of motor driven pulleys. One side of one dual leg of the drive lugged belt is twisted and opposite end belt connections are reversed for proper belt lug engagement with the lugged pulleys of each set pair of gear meshed pulleys. The lugged belt is attached to opposite ends of the "X" axis carriage with the opposite ends of the belt in close adjacency at one end of the "X" axis carriage and with the inside section of a belt loop segment clipped to the other end of the "X" axis carriage. In this drive system a driven member is moved independently in two mutually perpendicular axes that are directly belt driven by their respective motors with this specification directed primarily to the design of the "Y" axis drive that uses a lugged belt of substantial length. The effect of hysteresis (or backlash) is substantially reduced in this drive system with four precision spur gears attached to four rear lugged pulley drive shafts with each meshed set assuming precise synchronous counter-rotation of each set, This forces the lugged belt to remain synchronous within each belt sector minimizing the effect of belt stretch by dividing the "Y" axis lugged drive belt into effectively three independent sections.